For questions or comments on CN0269, please reply below
I've looked through the CN0269 schematics for the pinout for J6 (a 2x6 0.1 header). This appears in the gerbers (from .zip archive) but not in either the .pdf schematic or the PADS .sch logic. From the gerbers, it appears that this header (J6) might be connected to the DOT SPI lines. Any help would be appreciated.
Thanks a lot for your help to points out this issue. I would update the design support package as soon as possible.
Thank you for your interest in this circuit.
My pleasure to answer your question and help to solve your question.
The design package is updated on website. Please downloaded from the link below:
Sorry for the inconvenience.
Wish you all the best.
Got the update. Thanks for your help.
Robert A.Stachnik, M/S 183-401| Robert.A.Stachnik@jpl.nasa.gov
Jet Propulsion Laboratory, | Office: (818) 354-1921
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why there are two digital and analog GND joint point? (Such as P4 and P5) And they are not in top or bottom layer,.Is it a mistake?
In order to provide a short current back-path for ADC digital interface, we usually put a 0ohm resistor or the GND joint point, as used in this circuit, just under or near the ADC digital interface. The same way of thinking, Analog-Multiplexer has digital control logic as well as analog path just like the ADC. When driving the multiplexer switching with fast digital signal, we need to provide a short back path for the driving current near the multiplexer.
With best regards,
thanks for your answer
but base your words I have some other querstions:
such as if only one channel is sampled(no switch),in this situation two GND joint point is not a good way. So I must make my systerm always in a switch mode ?
Yes, you can only add one GND joint when your system never switching Multiplexer at high frequency but if your circuit need to scan all the channel one by one to realize the multi-channel DAQ system, you could follow the way CN0269 did. But to be honest, both way could work and without a big difference and the difference is hard to find out and usually ignorable.
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